I'm not a fan of kimberwickes. Tried one briefly, but if you want leverage, get a bit WITH a reasonable amount of leverage.
Leverage bits are not bad or evil. Horses are individuals, and some respond well to pressure on the poll. My mare will fight snaffles, but goes well in this:
It is a variation of a Billy Allen. The sides move independently, and there is a copper roller in the middle that prevents any nutcracker effect. But western curbs are designed for use with slack in the reins, and that may not suit your goals.
Bitless works well with some horses, and lots do fine in snaffles. Trooper uses a single-joint copper eggbutt snaffle and does great. I found it easier to keep Mia from rooting while cantering with the bit pictured above. I sometimes ride with an English saddle, but I use a western approach to reins ALL the time. Your needs may be very different from mine, though...so I'm just giving some options. Good luck with whatever you decide.